1. Field of the Invention
The present invention relates to an image forming method and apparatus of effectively removing toner. More particularly, the present invention relates to a cleaning device for removing toner from an image bearing member, an electrophotographic image forming apparatus including the cleaning device, and a method of controlling a cleaning operation for removing toner remaining on an image bearing member in the image forming apparatus.
2. Discussion of the Related Art
In general, background image forming apparatuses transfer a toner image formed on a surface of an image bearing member or a photoconductive element onto a primary transfer member or a recording medium. After the transfer operation has been completed, the background image forming apparatuses remove toner remaining on a surface of the image bearing member by a cleaning device employing a cleaning member.
Known cleaning devices use a cleaning blade as a cleaning member. The cleaning member is held in contact with the surface of the image bearing member so that the cleaning member can remove the toner remaining on the surface of the image bearing member.
To intermittently perform a cleaning operation with respect to the image bearing member, the cleaning device having the above-described cleaning member may employ a contact and separation mechanism so that the cleaning member can be separated from the image bearing member during a period in which the cleaning device is not in a cleaning operation. With such contact and separation mechanism, the cleaning device can effectively increase the life of the image bearing member and that of the cleaning member.
One known image forming apparatus with the above-described cleaning device employs a polishing device to prevent an image bearing member from deterioration, for example toner filming due to adhesion. Specifically, in addition to a cleaning device constantly removing residual toner from a surface of an image bearing member, the image forming apparatus includes a polishing device with a polishing blade and a driving unit that operates the polishing blade during a non-image forming operation.
A different background image forming apparatus is known to have a technique that can prevent the occurrence of a toner filming on an image bearing member for a long period of time and before the production of blurred images and the occurrence of image deletion. The background image forming apparatus employs a cleaning member including a cleaning blade with a polishing agent to remove residual toner from a surface of the image bearing member. The cleaning blade is held in contact with the surface of the image bearing member via the polishing agent, and the surface of the image bearing member is formed with a material having a hardness such that such surface cannot be damaged by the cleaning blade.
Further, a different background image forming apparatus using spherical and small toner particles is known to include a technique in which a cleaning device is provided to remove remaining toner and foreign material on the surface of the image bearing member and to maintain a cleaning ability for a long period of time. The cleaning device includes first and second cleaning blades in order from an upstream side of a rotational direction of the image bearing member. The second cleaning blade has a double-layered structure including a blade body layer and a layer having particles of the polishing agent.
The above-described background image forming apparatuses can, however, damage a surface of an image bearing member through cleaning operations performed by a cleaning device.
In recent years, transfer sheets include calcium carbonate for increasing its degree of whiteness, and various additives are added to the developer or toner for stabilizing the characteristics of toner. Since a great number of the components or additives is smaller in size and greater in hardness than those used before, a cleaning blade serving as a cleaning member is designed to be contacted with and separated from a surface of the image bearing member. When the smaller and harder components or additives included in toner and paper dust adhere to the edge of the cleaning blade of the cleaning device, the surface of the image bearing member can be damaged. When the surface of the image bearing member has scratches and damage, the surface potential of the damaged area of the surface thereof may become unstable, which may result in the production of defective images due to change in electrical potential.